The etymology of Christmas is unsurprising, though it had to be done today. Christmas is a combination of the Old English words Cristes and mæsse, which meant "Christ" and "mass", respectively (the latter in the biblical sense). Cristes comes from the Greek word khristos, which translated as "messiah" and had Hebrew origins. This went into Latin as christus and English as crist, and though it was originally just a title almost everybody thinks it was his last name. It's not; he had none. Mass did come from PIE, where it can be traced back to the word meith, which meant "to remove". This became the Latin word mittere, or "to send away", and this in turn was conjugated into Latin missa, with the defintion of "dismissal". Eventually this became mass, through some variations, including messa and maesse, with a significant definition change. The transition from "dismiss" to "mass" occurred because at a mass you would "send" or "dismiss" your prayers to God. It 's kind of funny, really, since the mass part of Christmas originally meant remove, and when you're saying Christmas, you're celebrating the Saviour a lot less than you're asking for his removal.
Adam Aleksic has been described as the internet's sixth most famous etymologist. He loves writing about himself in the third person, he's a freshman at Harvard University, and he has disturbing interests in linguistics, vexillology, geography, board games, limericks, and law.
The Etymology Nerd